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HowTo: Making a bootable ISO w/ miniroot.kmod etc.
I've asked how building a bootable ISO works now that we have kernel
modules and a bootloader that can load kernels before the kernel,
e.g. for a ramdisk. After some digging, I've managed to fit the pieces
together, get things going, and here is a write-up so others that
are intestested don't have to wade through that swamp again.
* build INSTALL kernel, which reserves fixed space for a ramdisk
image (pseudo-device md, options MEMORY_DISK_HOOKS,
MEMORY_DISK_IS_ROOT, MEMORY_DISK_SERVER=0, MEMORY_DISK_ROOT_SIZE)
* build ramdisk image (done in src/distrib/i386/ramdisks). This uses
crunchgen(1) and makefs(8) to assemble things, configuration is in one
or several "list" files.
* insert ramdisk image into kernel to get an instkernel (done in
src/distrib/i386/instkernel). This is done via mdsetimage(8).
* build ISO with instkernel and bootloderer (done in
src/distrib/i386/cdroms/bootcd). This uses makefs(8) again.
* build GENERIC kernel, which tells there will be a ramdisk, but size
will be detected at load-time (pseudo-device md, options
* build ramdisk image as before (in src/distrib/i386/ramdisks)
* build the miniroot.kmod (in src/sys/modules/miniroot). This is an
empty module for a start, which will get the ramdisk appended in
the next step.
* add the ramdisk image to the miniroot.kmod module (done in
src/distrib/i386/kmod). This uses the GNU bintools objcopy(1) to
append the ramdisk into a special ELF section.
* prepare an instkernel that is basically just a compressed version
of the GENERIC kernel (done in src/distrib/i386/instkernel). This
is the same code as before, but for each kernel, variables can be
set to prevent it from getting stripped and a ramdisk image
* build ISO with the instkernel kernel, the miniroot.kmod file, the
bootloader and a config file for the bootloader (done in
P.S.: I wonder if/how module loading works in a PXE boot environment.
anyone got experiences with that?
 g4u 2.4alpha3 is available for testing
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